title: Strain measurement in the left ventricle during systole with deformable image registration.
abstract: The objective of this study was to validate a deformable image registration technique, termed Hyperelastic Warping, for left ventricular strain measurement during systole using cine-gated, non-tagged MR images with strains measured from tagged MRI. The technique combines deformation from high resolution, non-tagged MR image data with a detailed computational model, including estimated myocardial material properties, fiber direction, and active fiber contraction, to provide a comprehensive description of myocardial contractile function. A normal volunteer (male, age 30) with no history of cardiac pathology was imaged with a 1.5 T Siemens Avanto clinical scanner using a TrueFISP imaging sequence and a 32-channel cardiac coil. Both tagged and non-tagged cine MR images were obtained. The Hyperelastic Warping solution was evolved using a series of non-tagged images in ten intermediate phases from end-diastole to end-systole. The solution may be considered as ten separate warping problems with multiple templates and targets. At each stage, an active contraction was initially applied to a finite element model, and then image-based warping penalty forces were utilized to generate the final registration. Warping results for circumferential strain (R(2)=0.75) and radial strain (R(2)=0.78) were strongly correlated with results obtained from tagged MR images analyzed with a Harmonic Phase (HARP) algorithm. Results for fiber stretch, LV twist, and transmural strain distributions were in good agreement with experimental values in the literature. In conclusion, Hyperelastic Warping provides a unique alternative for quantifying regional LV deformation during systole without the need for tags.
authors.affiliation: Department of Bioengineering, University of Utah, 50 South Central Campus Drive, Salt Lake City, UT 84112-9202, USA.
authors.forename: Nikhil S
authors.initials: NS
authors.lastname: Phatak
authors.forename: Steve A
authors.initials: SA
authors.lastname: Maas
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Veress
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Pack
authors.forename: Edward V R
authors.initials: EV
authors.lastname: Di Bella
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Weiss
mesh_terms: D000328:Adult; D000465:Algorithms; D003198:Computer Simulation; D055119:Elastic Modulus / Q000502:physiology; D054459:Elasticity Imaging Techniques / Q000379:methods*; D006352:Heart Ventricles / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008955:Models, Cardiovascular; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D016277:Ventricular Function, Left / Q000502:physiology*